
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 uv = (fragCoord.xy / iResolution.xy);
    vec4 particleColor = texture2D(iChannel0, uv);
    vec4 maskColor = texture2D(iChannel1, uv);
    vec4 faceColor = texture2D(iChannel2, uv);
    
    fragColor = mix(particleColor, faceColor, maskColor.r);
}
